Website accessibility and SEO: one site that works for every visitor and for Google.

When I build or review a site in my web design and development work, I check website accessibility and SEO in the same pass, because so many of the fixes are identical. A page that a screen reader can read clearly is usually a page Google can read clearly too.

What is an accessible website?

An accessible website is one that people with disabilities can perceive, understand, navigate and use: someone who is blind and uses a screen reader, someone who cannot use a mouse, someone with low vision who zooms in or someone who cannot hear. In practice, it means content and controls that do not depend on one single sense or device.

What is WCAG?

WCAG, the Web Content Accessibility Guidelines, is the international standard for web accessibility, developed by a working group of the W3C Web Accessibility Initiative. The latest version, WCAG 2.2, was published in October 2023. Its success criteria have three levels, A, AA and AAA, organized under four principles: perceivable, operable, understandable and robust.

The details are in the W3C's WCAG 2 overview. WCAG is written for developers and is long; owners do not need to read it end to end. Level AA is the level most organizations aim for, and the checklist below covers its most common items.

Does accessibility help SEO?

Indirectly, yes, because many accessibility requirements give search engines the same information they give assistive technology. Alt text describes images, headings outline the page, descriptive links say where they go and transcripts turn audio into text. Google does not publish accessibility as a ranking factor, so treat the SEO gain as a side effect, not the goal.

Alt text and headings: the two biggest overlaps

Alt text is the clearest case. Google's image SEO best practices say it uses alt text to understand images, and the W3C's alt decision tree explains when an image needs alt text and when it should be empty because it is decorative. I cover how to write it, with store examples, in image alt text for SEO.

Headings are the second. Screen reader users often move through a page by jumping from heading to heading, so an outline with one H1 and ordered H2s and H3s is a navigation tool for them, and a structure signal for search engines. The full how-to is in H1, H2 and H3 heading tags for SEO.

Why does link text matter for accessibility and SEO?

Screen reader users can pull up a list of every link on a page, read out of context. Ten links that all say "read more" are useless in that list. Google also uses the visible link text to understand the page being linked. A link like "see our pricing for local SEO" works for both; "click here" works for neither.

Google says this directly in its link best practices: anchor text should be descriptive and make sense on its own. The same goes for buttons: a button that only shows an icon needs an accessible label.

What color contrast does WCAG require?

At level AA, normal text needs a contrast ratio of at least 4.5 to 1 against its background, and large text at least 3 to 1. Light gray text on white, or text placed over a busy photo, often fails. Free contrast checkers tell you the ratio in seconds; you only need the two color codes.

The exact wording and exceptions are in the W3C's Understanding contrast (minimum). Contrast does not change rankings directly, but text people cannot read is text that does not sell.

Does the language attribute help SEO?

Not for language detection. Google says it uses the visible content of a page to determine its language and does not use code-level information such as lang attributes. Still set it: screen readers rely on the lang attribute to pronounce the text correctly, so a Spanish page marked as English is read with the wrong voice.

That statement comes from Google's guide to managing multi-regional and multilingual sites. For bilingual sites, hreflang does the SEO job and lang does the accessibility job.

A practical accessibility checklist for owners

The W3C publishes Easy Checks, a first review anyone can do without being a developer. These are the items I start with on a business website:

• Every page has a clear, unique title.
• Meaningful images have alt text; decorative images have empty alt.
• One H1 per page and headings in order, without skipping levels.
• Link and button text says where it goes or what it does.
• Text meets contrast: 4.5 to 1 for normal text.
• You can reach every menu, link and form field with the Tab key and see where the focus is.
• The page still works when zoomed to 200 percent on a desktop.
• Form fields have visible labels, not only placeholder text.
• Videos have captions; audio has a transcript.
• The page declares its language in the html tag.

Easy Checks are a starting point, not a full audit: the W3C notes that a more extensive assessment is needed to evaluate accessibility comprehensively. Automated tools catch some issues, such as missing alt text or low contrast, but not whether the alt text is actually useful.

Is website accessibility a legal requirement?

It depends on where you operate and what kind of organization you are, so check with your counsel. As information only: in the United States, the Department of Justice published guidance in 2022 saying its position is that the ADA applies to the web offerings of businesses open to the public, and it points to WCAG as helpful technical guidance.

You can read the Department of Justice's guidance on web accessibility and the ADA directly; it notes that guidance documents have no legally binding effect on their own. Other countries have their own rules. This article is not legal advice.

Where to start if your site was never built with accessibility in mind

Fix the templates first. On most sites, the header, menu, product or service template and footer appear on every page, so one fix in the template corrects hundreds of pages. Then fix the pages that bring customers: home, services, contact. Google's SEO Starter Guide gives the same advice for search: make the site useful and easy to use for people. If you are planning a new site, it is far cheaper to build accessibility in from the start, which I explain in why website design matters for SEO. As an SEO consultant who also builds websites, I can review both in a free diagnosis: book it here.

Frequently asked questions

About the author

Juan José Giraldo is an SEO consultant in Medellín, Colombia, with 5+ years of experience. He works on technical and local SEO for 600+ US car dealerships at Reunion Marketing, an Inc. 5000 agency, and supervises the SEO of 18 US online stores with more than 3 million products at Prontomowers. Read more · LinkedIn.

Sources

1. W3C Web Accessibility Initiative, WCAG 2 Overview
2. W3C Web Accessibility Initiative, Easy Checks: A First Review of Web Accessibility
3. W3C, Understanding Success Criterion 1.4.3: Contrast (Minimum)
4. U.S. Department of Justice, Guidance on Web Accessibility and the ADA (March 18, 2022)
5. Google Search Central, Managing multi-regional and multilingual sites
6. Google Search Central, Google image SEO best practices
7. W3C Web Accessibility Initiative, An alt decision tree
8. Google Search Central, Link best practices for Google
9. Google Search Central, SEO Starter Guide